When planning to install artificial grass, most people focus on the turf itself — its color, pile height, or softness. While the turf gives your lawn its look and feel, a properly prepared artificial grass base is essential for long-lasting performance.

A solid, well-constructed base provides the foundation for a smooth and stable lawn. It supports drainage, helps reduce weed growth when combined with suitable weed-control measures, and reduces the risk of sinking, shifting, or uneven spots.

So, what do you put under artificial grass?

Quick Answer

For most artificial grass installations over soil, a compacted aggregate sub-base topped with a thin leveling layer provides a stable, smooth foundation. A weed membrane may also be used to help control weed growth.

In this article:

Overview: Key components under artificial grass

Before diving into materials and methods, here’s a quick look at the structure beneath a typical artificial lawn:

Layer	Main Purpose	Common Materials
1. Weed Barrier	Weed prevention	Geotextile fabric, mesh weed membrane
2. Sub-base	Stability & Drainage	Crushed stone, decomposed granite
3. Levelling Layer	Smooth surface	Sharp sand, granite dust
4. Optional layer	Extra cushioning or drainage	Shock pads, drainage mats

These components serve different purposes in an artificial grass installation. The following sections explain their roles and how to choose suitable materials.

Weed membrane: Stop unwanted growth

A weed membrane is recommended when installing artificial grass over natural soil, especially in areas prone to weed growth. It blocks unwanted vegetation and keeps the sub-base separate from the soil, maintaining stability and proper drainage.

Types of weed membrane

Woven geotextile fabric: Durable and ideal for high-use or heavy-traffic areas.
Non-woven fabric: Lightweight, cost-effective, and easy to handle for residential installations.

Installation tips

Prepare, level, and compact the soil before laying the weed-control membrane. Spread the fabric evenly over the prepared ground, keeping it flat and free of wrinkles.
Overlap each section by 2–3 inches to ensure full coverage and prevent weeds from finding gaps.
Secure the fabric with landscape pins or galvanized nails to keep it firmly in place.

Note: Some installers prefer to omit the weed membrane when installing pet-friendly artificial grass to help reduce the risk of odor buildup from pet urine. In such cases, a properly prepared and compacted sub-base, combined with appropriate weed-control measures, can help limit weed growth.

Artificial grass base: Build a strong and smooth foundation

The sub-base and leveling layer provide the main support for your turf, ensuring proper drainage and a smooth, even surface. Choosing the right materials is essential—so, what is the best base for artificial turf?

Sub-base: Stability & drainage

The sub-base is the primary load-bearing layer of your artificial grass installation. Its critical role is to create a stable foundation that resists shifting or settling, while ensuring efficient water drainage away from the surface.

Recommended materials for the sub-base

Crushed stone – A widely used choice

Crushed stone for artificial grass bases typically consists of angular aggregate, sometimes blended with finer particles. A suitable grade can compact into a stable sub-base while allowing water to drain through.

Key advantages:

Superior stability: The jagged particles interlock tightly when compacted, forming a rigid, interlocking structure that resists movement and settling even under heavy loads.
Good drainage: The aggregate base allows water to pass through, helping reduce water accumulation beneath the turf.
Ideal for: Most installations, especially high-traffic areas, regions with frequent rainfall, and projects requiring long-term durability.

Decomposed granite (DG)

DG is a sandy, granular material produced by the natural weathering of granite. It can perform well in the right conditions but requires careful consideration of the site environment.

Key advantage: Can form a firm, relatively smooth base when properly compacted, providing an even surface for turf installation.

Important considerations: Because of its higher fines content, DG drains more slowly than crushed stone and can soften slightly when saturated. It’s best suited for well-drained soils and arid climates.

Sub-base installation tips

Compact in layers: For optimal stability, spread and compact the aggregate in thin layers—typically 2 to 3 inches (5–7.5 cm) per lift when using a plate compactor.
Moisture control: Lightly mist the aggregate to make it slightly damp; this helps bind fine particles for maximum compaction without muddying the subgrade.
Slope for drainage: Ensure the final sub-base has a gentle slope (typically 1–2%) directing water runoff toward a suitable drainage outlet and away from building foundations.

Leveling layer: The perfect finish

Once the sub-base is fully compacted, the leveling layer is applied. This final course creates a perfectly smooth surface, allowing the turf to lie flat, feel comfortable underfoot, and facilitate surface drainage.

Recommended materials for the leveling layer

Sharp sand or concrete sand

A coarse, washed sand with angular grains — one of the most popular materials for creating a smooth and stable finish.

Key advantages:

Workability: Easy to spread and screed for precise leveling.
Drainage: The angular structure remains porous, allowing water to pass through efficiently.

Granite dust (stone dust)

A byproduct of stone crushing, consisting of fine particles and dust. It produces an exceptionally smooth and firm surface.

Key advantage: Excellent for filling minor imperfections and ensuring a dense, ultra-smooth surface.

Important consideration: Granite dust can be less permeable than suitable sharp sand, depending on its grading and fines content. Use it in a thin layer over a well-draining sub-base.

Tips for a perfect finish

Use suitable sharp sand or granite fines rather than topsoil or unsuitable fine material that may retain moisture or shift beneath the turf.
Use a screed board or straightedge to create a smooth, even surface.
Compact or settle the leveling material as appropriate for the material and installation method, without disturbing the finished surface.

How deep should each layer be?

For many residential lawns, a compacted crushed aggregate sub-base of around 2–3 inches (50–75 mm) may be suitable. Areas with poor drainage, unstable soil, or heavier use may require 3–4 inches (75–100 mm), depending on site conditions.

A thin leveling layer of around ⅜–½ inch (10–15 mm) of granite fines or suitable sharp sand can then be added over the compacted sub-base to create a smooth, even surface beneath the turf.

When installing artificial grass over existing concrete, balconies, or rooftops, excavation and a conventional aggregate sub-base are usually unnecessary. Instead, the existing surface, drainage conditions, and chosen installation system determine whether additional leveling or drainage layers are needed.

Optional cushion & drainage layers

Cushion and drainage layers are not required for every installation, but they can be useful depending on the project type.

Shock pad / foam underlay

Adds extra softness and impact absorption, ideal for playgrounds, gyms, or pet zones.
Reduces stress on joints and provides a natural feel underfoot.
Useful when installing over hard surfaces like concrete to smooth minor imperfections.

Drainage tiles

Designed for installations on rooftops, balconies, or concrete surfaces.
Improve water runoff and allow airflow beneath the turf.
Easy to install — simply snap together the modular panels.

If the existing surface already drains well, a drainage layer is not necessary.

Frequently asked questions

Can you lay artificial grass directly on soil?

Directly laying artificial grass on soil is not recommended for most installations. The ground should be properly prepared and stabilized before installation. Laying turf over loose or uneven soil can lead to an uneven surface, ground settlement, and drainage problems.

Do you need sand under artificial grass?

Not always. A thin leveling layer of suitable sharp sand or fine aggregate may be used over a compacted sub-base to create a smooth, even surface, depending on the installation method. Sand alone cannot replace a stable, compacted sub-base.

What do you put under artificial grass on concrete?

Artificial grass can often be installed directly over sound, suitably sloped concrete without a conventional aggregate sub-base. Depending on the surface condition, drainage, and intended use, a drainage mat or suitable underlay may be added. Ensure that water has a suitable route to drain away before installation.

For more details, see our guide to installing artificial grass on concrete.

Conclusion

The secret to a beautiful and long-lasting artificial lawn lies in what’s underneath it.

Understanding the role of the sub-base, leveling layer, and optional weed-control membrane can help you build a stable foundation for artificial grass. Additional cushion or drainage layers may be useful for certain applications.

Whether it’s a home garden, playground, or pet area, taking the time to build a reliable base will ensure your artificial grass stays smooth, stable, and easy to maintain for years to come.

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